ONAN Marquis Gold 7000 Gas

Rich Biebel · 08-07-2019, 05:53 PM

Did one today. Coupler broke. Pulled machine out yesterday afternoon after reinstalling an old BGE in an old motorhome.
Had it cleaned up and back together and running today by early afternoon.
Load tested it for a while.
Got sidetracked fixing another one with random shutdowns.
Replaced control board on that one.
Rain prevented me from reinstalling first one.
Will complete it tomorrow and then on to a diesel 5.5 and others waiting in the wings.
Pretty much non stop lately.....

Hacksaw · 08-09-2019, 09:52 AM

I think a valuable lesson can be learned here. Because most large coach style gensets are such an animal to r & r from the coach, it would be wise to take the extra time to test before you reinstall. Now a guy like Rich is set up for this and he routinely does this probably because he has been thru this problem before.

voltdr · 08-17-2019, 09:58 PM

I agree completely. While I don't have a way to load test the unit. Before I installed it the second time, I hooked up a fuel line and a battery and started it to make sure it was going to run. Yes, I should've done that the first time, but I was "certain" I had everything right..........LOL
Dan

voltdr · 09-07-2019, 11:30 AM

I wanted to give everyone an update on the generator repairs. Went to Bowling Green, then INDY. Genset worked perfectly. I adjust the governor for 62 Hz, no load, and everything worked like new. Thanks to Rich and all who made comments. Looking forward to another 7500+ more hours.
Dan

Rich Biebel · 09-07-2019, 07:00 PM

Yesterday I spent 2-3 hours working on a commercial van with an Onan 7KW gas generator just to make a diagnosis on what was wrong.

I always say there is nothing I haven't seen but yesterday was a new one.

Power in the van would out of nowhere go off or erratically drop.

Generator never gave any indication it was the problem.

Van had a Automatic Transfer Switch and one very common in RV's

AC power in that switch from the generator was never lost going by my Fluke Meter....

The ATS was mounted in a difficult to get at location and after some time I felt like it was the issue...I bypasses it by connecting the generator output straight thru to the load side that fed a breaker panel. Easy to do right in the switch. Would order one and replace it at a later time...

That was the plan....but no....

The problem got worse and now the generator was shutting down and triggering codes.....???

I rechecked my connections and nothing was wrong....

Now I start to think it is the generator itself and that is exactly what was wrong...

The Control board is also the voltage regulator and even though voltage always showed up on my Fluke meter.....once any kind of load was applied AC output would fade.

I swapped in a test Control board and problem was gone. Old board had obvious issues that caused potting material to overheat and melt...

That was the first time I had ever seen a behavior like this one and shows how easy it can be to really chase a problem with a generator in a motorhome/trailer or any vehicle with the added equipment connected down stream from the generator.....

voltdr · 09-13-2019, 10:58 AM

Thanks for the story. I like to hear everything that may help me to diagnose a problem in the future. AC (especially 3-phase) can send you in circles troubleshooting. I just had this kind of experience with a customer's submersible pump in a 10K diesel tank.
Thanks again for sharing your knowledge with us.
Dan

Rod Greene · 09-14-2019, 02:51 PM

This is off topic but about generators. I read on here all the time of guys having problems with their ONAN gens. A friend has an Onan and has changed that board many times. If you were building a coach is there a diesel gen that is reliable?

08-07-2019, 05:53 PM	#1
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,319 Likes: 25 Liked 551 Times in 215 Posts	Re: ONAN Marquis Gold 7000 Gas Did one today. Coupler broke. Pulled machine out yesterday afternoon after reinstalling an old BGE in an old motorhome. Had it cleaned up and back together and running today by early afternoon. Load tested it for a while. Got sidetracked fixing another one with random shutdowns. Replaced control board on that one. Rain prevented me from reinstalling first one. Will complete it tomorrow and then on to a diesel 5.5 and others waiting in the wings. Pretty much non stop lately..... __________________ Rich Biebel S/C 1479 Stock 147R

08-09-2019, 09:52 AM	#2
Hacksaw Senior Member Join Date: Sep 2016 Posts: 884 Likes: 209 Liked 312 Times in 175 Posts	Re: ONAN Marquis Gold 7000 Gas I think a valuable lesson can be learned here. Because most large coach style gensets are such an animal to r & r from the coach, it would be wise to take the extra time to test before you reinstall. Now a guy like Rich is set up for this and he routinely does this probably because he has been thru this problem before.

08-17-2019, 09:58 PM	#3
voltdr Senior Member Join Date: Jan 2008 Location: Texas Posts: 706 Likes: 77 Liked 100 Times in 51 Posts	Re: ONAN Marquis Gold 7000 Gas I agree completely. While I don't have a way to load test the unit. Before I installed it the second time, I hooked up a fuel line and a battery and started it to make sure it was going to run. Yes, I should've done that the first time, but I was "certain" I had everything right..........LOL Dan __________________ Dan Foley SC 4698

09-07-2019, 11:30 AM	#4
voltdr Senior Member Join Date: Jan 2008 Location: Texas Posts: 706 Likes: 77 Liked 100 Times in 51 Posts	Re: ONAN Marquis Gold 7000 Gas I wanted to give everyone an update on the generator repairs. Went to Bowling Green, then INDY. Genset worked perfectly. I adjust the governor for 62 Hz, no load, and everything worked like new. Thanks to Rich and all who made comments. Looking forward to another 7500+ more hours. Dan __________________ Dan Foley SC 4698

09-07-2019, 07:00 PM	#5
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,319 Likes: 25 Liked 551 Times in 215 Posts	Re: ONAN Marquis Gold 7000 Gas Yesterday I spent 2-3 hours working on a commercial van with an Onan 7KW gas generator just to make a diagnosis on what was wrong. I always say there is nothing I haven't seen but yesterday was a new one. Power in the van would out of nowhere go off or erratically drop. Generator never gave any indication it was the problem. Van had a Automatic Transfer Switch and one very common in RV's AC power in that switch from the generator was never lost going by my Fluke Meter.... The ATS was mounted in a difficult to get at location and after some time I felt like it was the issue...I bypasses it by connecting the generator output straight thru to the load side that fed a breaker panel. Easy to do right in the switch. Would order one and replace it at a later time... That was the plan....but no.... The problem got worse and now the generator was shutting down and triggering codes.....??? I rechecked my connections and nothing was wrong.... Now I start to think it is the generator itself and that is exactly what was wrong... The Control board is also the voltage regulator and even though voltage always showed up on my Fluke meter.....once any kind of load was applied AC output would fade. I swapped in a test Control board and problem was gone. Old board had obvious issues that caused potting material to overheat and melt... That was the first time I had ever seen a behavior like this one and shows how easy it can be to really chase a problem with a generator in a motorhome/trailer or any vehicle with the added equipment connected down stream from the generator..... __________________ Rich Biebel S/C 1479 Stock 147R

09-13-2019, 10:58 AM	#6
voltdr Senior Member Join Date: Jan 2008 Location: Texas Posts: 706 Likes: 77 Liked 100 Times in 51 Posts	Re: ONAN Marquis Gold 7000 Gas Thanks for the story. I like to hear everything that may help me to diagnose a problem in the future. AC (especially 3-phase) can send you in circles troubleshooting. I just had this kind of experience with a customer's submersible pump in a 10K diesel tank. Thanks again for sharing your knowledge with us. Dan __________________ Dan Foley SC 4698

09-14-2019, 02:51 PM	#7
Rod Greene Senior Member Join Date: Mar 2002 Location: TN Posts: 530 Likes: 431 Liked 242 Times in 81 Posts	Re: ONAN Marquis Gold 7000 Gas This is off topic but about generators. I read on here all the time of guys having problems with their ONAN gens. A friend has an Onan and has changed that board many times. If you were building a coach is there a diesel gen that is reliable? __________________ Rod Greene Real men shift for them selves. Slowly working on TA Challenger for D,E/S and a 72 Challenger for SS/K, L as if I don't have enough other projects.